1. Field of the Invention
The present invention relates to an apparatus and a method for filtering an Internet Protocol (IP) packet in a mobile communication terminal. More particularly, the present invention relates to an apparatus and a method for reducing unnecessary current consumption through IP packet filtering in an always-on mobile communication terminal including two Central Processing Units (CPUs).
2. Description of the Related Art
Recently, the number of mobile apparatuses using a high performance open Operating System (OS) including two CPUs is increasing. Such mobile apparatuses are characterized by always-on operation that maintains an open data session in order to support functions such as a Voice over Internet Protocol (VoIP), a mobile messenger, a push mail, etc.
A terminal using a Wideband Code Division Multiple Access (WCDMA) system is allocated an IP address from a service provider network. In most cases, the allocated IP address is a public IP. An always-on terminal that has been allocated a public IP is exposed to an undesired Transmission Control Protocol (TCP) connection request from an external network. The terminal is connected to a radio channel due to introduced IP packets at this point, and causes current consumption. In addition, for push mail, a push mail application releases a radio channel after packet transmission ends, but when a radio channel is connected due to IP packets introduced by the undesired TCP connection request, an entity that releases the radio channel does not exist and so additional current consumption occurs until a network timer ends.
An IP packet introduction scenario of an always-on terminal including two CPUs according to the conventional art is described below. After a Packet Data Protocol (PDP) context is generated, a terminal and a mobile network enter a Radio Resource Control (RRC) idle state. In this RRC idle state, when an IP packet for a TCP connection request is introduced to the mobile network from an external server, the mobile network transmits a Packet Switched (PS) paging message to the terminal. Accordingly, the terminal and the mobile network transition to an RRC connected state. In this RRC connected state, the mobile network transmits an IP packet introduced from the external server to the terminal, and a modem of the terminal transfers an IP packet received from the mobile network to an application CPU of the terminal. A TCP stack of the application CPU side of the terminal determines that the relevant IP packet is an IP packet for an undesired TCP connection request and transmits an IP packet for TCP reset to the external server via the mobile network, thereby rejecting a TCP connection request from the external server. The terminal and the mobile network maintain RRC connection state for one minute generally until a timer of the mobile network ends.
As described above, since a TCP stack exists at an application CPU side in an always-on terminal including two CPUs, an IP packet introduced from an external server is transferred to the application CPU without filtering, and an RRC connection is not immediately released even after TCP connection request rejection and maintained until the RRC connection is ended by a mobile network, and so current consumption occurs continuously.